Process for desulphurization of hydrocarbons



y 9, 1940- w. A. SCHULZE I 2,206,921

PROCESS FOR DESULPHURIZATION OF HYDROCARBONS Original Filed Oci. 6, 1936HEATED v DESULFURIZED GASOLINE GASOLINE VAPORS TO STORAGE u- N CATALYSTCHEMICAL TOWER TREATIN 6 UNIT on FRACTIONATING UNIT INVENTOR. w. A. SCHULZE BYLLM-M m A TTORNEYS.

Patented July 9, 1940 UNITED STATES,

PROCESS FOR DESULPHURIZATION OF HYDROCARBONS Walter A. Schulze,Bartlesville, kla., assignor to Phillips Petroleum Company, acorporation oi. Delaware Application October 6,

1936, Serial No. 104,304

Renewed July 1, 1939 3 Claims.

This invention relates to the treatment of hydrocarbons and relates moreparticularly to catalytic methods of treating petroleum fluids such asstraight run and cracked gasolines, pressure 5 distillates, naphthas,polymerized gasolines and natural gasolines, such petroleum fluids beingreferred to hereafter as gasoline stock.

Applicants co-pending application Serial No. 104,303 relates to reducingpoisoning of catalysts, and Serial No. 104,306 relates to catalytictreatment of oils with a bauxite catalyst.

In a more specific sense an object of this invention is a process fortreating such potential motor fuel components in the vapor form over acatalytic material to remove the organic sulphur compounds which are sodeleterious to the octane number and lead response of such fuels.

Another object of the invention is a process for treating gasoline stockin the vapor form over a catalytic material to reduce its sulphurcontent and simultaneously increase its octane number, improve itsantiknock characteristics and otherwise produce desirable refiningeffects.

A further object of this invention is the marked improvement in qualityof the gasoline stock with only a small decrease in volume of productboiling within the same range as the untreated oil. This is incontradistinction to the large losses which occur in such conventionaloperations as thermal reforming of such oils.

A still further object of the invention is the production under certainconditions of a gasoline stock with both a higher specific gravity and ahigher octane rating than the untreated stock, whereas cracking of oilsin the established manner produces higher octane products but of lowerspecific gravity.

Another object of the invention is the production under certainconditions of a by-product gas 40 relatively rich in hydrogen, such gasbeing quite useful in hydrogenation processes as well as for many otherpurposes.

It is well known that motor fuel specifications call for much higheroctane ratings now than 45 formerly, and gasoline stocks are beingsubjected to extensive refining and reforming operations in order tomeet these more rigid specifications. Since the advent of Q" gasolineseveral years ago, large quantities of tetraethyl lead, also, have 50been added to gasolines to raise them to 70 octane number, the rating ofthe average house-brand gasoline at the present time. All of thesepractices are quite expensive.

More recently certain results showing the 55 deleterious efiects ofimpurities of the sulphur type on the octane number and lead response ofmotor fuels were published in an article by Schulze and Buell (Oil andGas Journal, vol. 34, No. 21, p. 22 (1935)). Organic sulphur compoundsof dif- 60 ferent types exist in varying percentages in all gasolinestocksand are present in unusually large amounts in those from WestTexas and certain other regions. The form of combination of the sulphuralso varies, e. g., mercaptans, alkyl sulphides, thiophenes andthiophanes. Some of these compounds are much more deleterious thanothers to the octane number and lead response of the motor fuels; hencethe magnitude of the reduction in sulphur content may or may not be acriterion of the improvement. in antiknock characteristics.

Schulze and Buell in an application, Serial No. 756,142, filed December5, 1934, describe certain catalytic processes for removing theseimpurities from sulphur bearing petroleum oils, thereby obtaining markedimprovement in octane number and lead response of such products asnatural gasoline and refinery straight run, cracked and vapor recoverygasolines.

I have now discovered a rather superior catalytic material for efiectingthe decomposition of the deleterious organic sulphur compounds inhydrocarbon oils and gases. Solid adsorbent catalytic materialconsisting of zirconium oxide either alone or in admixture with aluminacauses rapid decomposition of mercaptans, organic sulphides and the liketo hydrogen sulphide when hydrocarbon vapors containing such impuritiesare passed over these contact masses. The zirconium oxide may besynthetically prepared or the naturally occurring minerals may be used,the latter not being quite as eiiective as the former. The zirconiumoxide gel may, if desired, be mixed with other metallic oxides orimpregnated with solutions of salts which may be subsequently reduced tothe oxide form.

A typical process for simple desulphurization of gasoline stock consistsin contacting the gasoline stock in vapor form at a temperature in therange of about 500 to 800 F. which eliminates a part or all of thesulphur from mercaptans, alkyl sulphides, etc., as hydrogen sulphide.The hydrocarbons are then freed of hydrogen sulphide by a caustic washor other suitable means. Completely sweetened products can be obtainedin this manner. The following example is given as merely illustrative ofthe results obtained by this invention and shall in no sense beinterpreted as a limitation of. the invention.

Composite cracked gasoline from Panhandle topped crude was contactedwith zirconium oxide catalyst at a temperature of 735 F. and a flow rateof about three liquid volumes per hour per volume of catalyst. Forcomparative purposes, another portion of the gasoline was treated undersimilar conditions with bauxite. A considerable improvement in leadresponse resulted with the bauxite treatment but the zirconia gave evena greater one. The decomposed impurities were removed in each instanceprior to determination of octane ratings.

One form of apparatus in which my desulphurization process may becarried out is illustrated in the drawing, Figure 1. In this drawing thecatalyst tower l containing the mass of catalyst receives the heated rawgasoline vapors from a vaporizing and heating device not shown. Afterpassage through the catalyst the treated vapors may be sent to thechemical treating unit 2. (2 may instead be a fractionating unit for ineither case the function of this part of apparatus is the removal ofhydrogen sulphide formed in the desulphurization reaction.)

I have discovered also that still greater improvement in antiknockcharacteristics can be obtained when the gasoline stocks are treatedunder the conditions specified below. In addition to the removal of theorganic sulphur impurities which are so deleterious to the octane numberand lead response of the gasoline stock, or the motor fuel madetherefrom, certain reactions which involve still other deleteriousimpurities and/or low octane number compounds are made to take placewhile in contact with catalysts comprising zirconia; therefore, thetreated product has an octane number considerably higher than thatproduced merely by the removal of the organic sulphur.

In one specific embodiment of this process which yields the combinedadvantages noted above, the gasoline stock is passed in the vapor formover a well dehydrated zirconium oxide catalyst at a temperature in therange of about 900 F. to 1200 F. and at a flow rate of 1 to 100 liquidvolumes per hour per volume of catalyst. For example, at a temperatureof 1000" F. to 1025 F. the preferred flow rate is of the order of 1 to10 liquid volumes per hour per volume of catalyst. At highertemperatures shorter contact times are sufficient; therefore, flow ratesas high as 100 liquid volumes per hour per volume of catalyst may beemployed.

I have discovered that in treating gasoline stocks in the vapor formover zirconia catalyst there are specific temperature ranges for thereactions involving the decomposition of those compounds responsible forthe low octane rating of the gasoline. As stated above, at temperaturesof 500 to 800 F. the organic sulphur compounds such as mercaptans, alkylsulphides, etc., are decomposed into hydrogen sulphide without anysubstantial decomposition of the hydrocarbon constituents, attemperatures in the range of 800 to 900 F. there is little or noadditional improvement in octane number over that obtained in the simpledesulphurization treatment, but at temperatures above 900 F. a secondseries of reactions takes place as evidenced by the formation of largequantities of hydrogen gas and by the marked increase in octane numberof the treated gasoline stock.

This marked improvement in octane number which results from thetreatment at temperatures above 900 F. is not due to cracking in theusual sense of the word, since in the absence of the zirconia catalystand under otherwise similar conditions of temperature and contact timethere is no appreciable change in the characteristics of the gasolinestock. Furthermore, the improvement which results from the treatmentwith zirconia catalysts under the conditions mentioned is not due to anaccelerated reforming similar to that occasioned by the presence ofadsorbent porous material sometimes referred to as material of the claytype. For example, when the same gasoline stock is contacted at thesetemperatures above 900 F. with fullers earth under identical conditionsof temperature, pressure and contact time the improvement is almost nilas compared with that obtained with the zirconia catalysts.

In the operation of this process high pressures are not needed,extremely good results being obtained in the range of atmospheric to 100pounds. Higher or lower pressures may of course, be employed wherevereconomic conditions warrant them. In practice it is usually desirable touse pressures somewhat above atmospheric so that the vapors can beconducted directly to a fractionator or to treating tanks for finalprocessing.

Following the treatment of the vapors over the catalyst the decomposedimpurities and light gas fraction are separated from the gasolinehydrocarbons by fractional condensation or any other conventional means.If desired, the uncondensed light gas fraction may be passed through avapor recovery plant of the absorption or other conventional typewhereby the hydrocarbons other than methane may be recovered and madeuseful for other purposes. Also the decomposed impurities may be removedby chemical means in a step apart from that of removal of the hydrogenand low boiling hydrocarbons from the gasoline hydrocarbons.

A typical example of the operation of this process above 900 F. is givenas illustrative of the results which have been obtained in the treatmentof various gasoline stocks, but this example is in no sense to beinterpreted as limiting the invention.

Refinery high end-point straight run gasoline from Panhandle crude oilwas contacted in the vapor form with dehydrated zirconia catalystmaintained at a temperature of 1000 F. and a flow rate of about 2volumes of liquid gasoline per hour per volume of catalyst. Afterremoval of the decomposed impurities and the light gas fraction byfractionation or any other conventional means the following remarkableimprovement was noted.

Before After treatment treatment A. S. T. M. octane number (0 cc. TEL).46.8 57.3

A. B. T. M.octane number with 1.0 cc. TEL. 55. 7 67.9

A. S. T. M. octane number with 2.0 cc. TEL- 60. 9 73. 7

A. S. T. M. octane number with 3.0 cc. TEL 65. l 76. 8

Reid vapor pressur 7. 80 9. 75

Unsaturation-... .mol percent. 0. 2 6. 4 Engler distillation:

10% evaporated F. 156 151 50% evaporated F. 255 246 95% evaporated .F.394 395 The fixed gas formed during the treatment of this gasolineamounted to 235 cu. ft. (S. T. P)

cent. The hydrogen amounted to i68cubic feet per barrel of gasoline andthe methane to 34 cubic feet, a hydrogen to methane ratio of 4.9. Thegas loss calculated as weight per cent of the The total loss in volumeof gasoline boiling within the same range as the untreated was about 3per cent. By this treatment the gasoline was made into a 70 octanenumbermotor fuel merely by adding 1.33 cc. of tetraethyl lead (TEL) pergallon whereas the untreated gasoline made only a 65 octane number motorfuel with the addition of 3 cc. tetraethyl lead (TEL) per gallon.

I have found that in the treatment of gasoline stocks in the vapor formover zirconia catalysts in the temperature range of 900 to 1200 F., as

shown in the example given above, considerable dehydrogenation of thehydrocarbons occurs. There is only a very slight amount of cracking, asevidenced by the small proportion of methane in the gas, providing, ofcourse, the temperature and contact time are properly chosen, since itis obvious that substantially long contact times at temperatures of 1100F. and above will produce cracking. With proper choice of thetemperature and contact time, however, it is possible by means of thisinvention to substantially avoid the formation of methane and otherproducts of cracking. Hydrogen to'methane ratios as high as 30 to 1, andsometimes higher, can readily be obtained.

I have found that although dehydrogenation of certain of thehydrocarbons occurs during the treatment of gasoline stocks withzirconia catalysts at temperatures above 900 F., this dehydrogenation isonly one of several reactions taking place. It is evident from theresults such as those given above that 'an improvement of 19.5 octanenumbers could not have resulted merely by the conversion of 6.5 per centof saturated aliphatic hydrocarbons to simple unsaturated hydrocarbonsof the olefin type. Neither can it be accounted for on the basis of theamount of hydrogen formed. While I am not certain of the exact changeswhich occur during this treatment of gasoline stocks over a catalyst ofthe peculiar nature of zirconium oxide, I believe the remarkableimprovement in octane number results from several concurrent reactions,namely, (1) decomposition of deleterious organic sulphur compounds tohydrogen sulphide'which may .be removed, (2) decomposition andsubsequent removal of impurities other than the sulphur type, (3)dehydrogenation of hydrocarbon constituents, and (4) changes inmolecular structure of certain of the hydrocarbons. The extent of theimprovement from each of these sources varies,

of course, with the gasoline stock being treated.

In the practice of the present invention the zirconium oxide or thezirconialike material is crushed to a suitable size, usually to 30 mesh.If desired it may be diluted with active or inactive substances.Particularly active catalytic masses may be prepared from intimatemixtures of zirconia and alumina gels. Either one of these gelsimpregnated with a salt solution of the other gives on drying and onconversion of the salt to the oxide form a very' satisfactory catalyst.Bauxite impregnated with a solution of am- 3 conium salt. usuallyconvertedto the oxide in a subsequent step. has high activity.

synthetic zirconium hydroxide gel usually contains a large proportion ofwater which is driven oil by heating at elevated temperatures. In thepractice of my process for the treatment of gasoline stocks to obtaindesulphurization, dehydrogenation and the like concurrently, bestresults are obtained with rather thoroughly dehydrated zirconiacatalysts. The first step in this process usually conslstsptherefore, indehydrating the zirconia, preferably in situ, by raising the temperaturegradually to the temperature of operation or higher while a slow streamof air or hy-' drocarbon gas is passed over it. Vacuum drying may bedone, if desired. This step of passing air or hydrocarbon gas over thecatalyst can obviously be omitted in practice, and the gasoline vaporsstarted immediately over the zirconia. Much of the improvement in thegasoline stock will be lost, of course, during the first few hours ofoperation in this manner, or until the workingtemperature has beenreached and the catalyst has been dehydrated.

It has been found that the zirconia catalysts gradually lose theircatalytic activity with use but they may be reactivated indefinitely byburning out the carbonaceous residues in situ with steam and air, or anoxidizing gas, or by recycled through the system by adding such gas,

or a, portion of it, to the gasoline vapors prior to passage over thecatalyst. Such hydrogen gas should, of course. not be allowed to pyramidtoo much or the reactions may be unfavorably influenced. Also inprocessing gasoline stocks containing appreciable quantities of sulphurcompounds, the hydrogen sulphide should be removed" from the gas priorto recycling.

Obviously the hydrogen gas produced as a by-product in my process hasconsiderable economic value. A gas containing up to 95 per cent hydrogenand the balance methane can be readily obtained by applying simpleextraction methods for the removal of the small amount of hydrocarbonshigher than methane. Concentrations of hydrogen higher than 95 per centcan be obtained by more elaborate extraction methods. In any eventhydrogen for hydrogenation and/or other purposes can be obtained in thistreatment of gasoline stocks over zirconia catalysts at extremely lowcost. A very distinct advantage of my process is the formation ofrelatively large quantities of hydrogen from such hydrocarbons as thoseof the aliphatic series with methane being the only impurity inappreciable amount. Obviously this gas can be utilized for many purposeswhere the more common mixture of hydrogen and carbon monoxide cannot betolerated at any cost.

If desired, the gasoline stock vapors may be given two or moresuccessive treatments with the zirconia catalytic material in a seriesof catalyst towers, or the vapors or any fraction thereof may berecycled with the fresh vapors through the catalyst tower. Someadditional heat, also, may be supplied to the vapors prior to the secondand/or successive catalytic treatments.

The gasoline stocks after treatment at desulphurizing temperatures of500 to 800 F. may or may not need a subsequent treatment to removecolored and gum forming constituents. At temmake them suitable as motorfuel.

it is of generally wide application and the number of examples oi.results obtainable by its use might be multiplied greatly neither is tobe construed as imposing limitations upon the scope of the invention.The term gasoline stocks as used herein includes natural gasolines,refinery straight run, cracked and vapor recovery gasolines, polymerizedgasolines, naphthas, pressure distillates,

and/or mixtures or blends of any two or more of these or of similarhydrocarbon mixtures. Light gases associated with such stocks may betreated along with the hydrocarbons boiling within the gasoline range,or, ii desired, such gases may be treated alone.

I claim as my ivention:

l. The process or desulphurizing a gasoline stock containing organicsulphur compounds as impurities, comprising contacting the said gasolinestock in the vapor form at a pressure between atmospheric and pounds persquare inch with a zirconium oxide catalyst at a temperature in therange of 500 to 800 F. and a flow rate equivalent to about three liquidvolumes of gasoline stock per hour per volume of catalyst, whereby asubstantial proportion of the organic sulphur compounds are decomposedinto hydrogen sulphide without any substantial decomposition of thehydrocarbon constituents, separating the hydrogen sulphide from thegasoline stock, and thereby obtaining a gasoline stock with a loweredsulphur content and improved response to tetraethyl lead.

2. The process of sweetening a gasoline stock containing organic sulphurcompounds of the mercaptan type, comprising contacting the said gasolinestock in the vapor form at a pressure between atmospheric and 100 poundsper square inch with a zirconium oxide catalyst at a temperature in therange of about 500 to 800 1". and a flow rateequivalent to about threeliquid volumes 0! gasoline stock per hour per volume of catalyst,whereby the mercaptans are converted into hydrogen sulphide, separatingthe hydrogen sulphide from the gasoline stock, and thereby obtaining asweetened gasoline stock.

3. The process of desulphurizing a gasoline stock containing organicsulphur compounds as impurities, comprising contacting the said gasolinestock in the vapor form at a pressure between atmospheric and 100 poundsper square inch with zirconium oxide catalyst at a temperature in therange oi. about 500 to 800 F. for a period of time sufficient to causedecomposition of a substantial proportion of the organic sulphurcompounds into hydrogensulphide but insuillcient time to cause anysubstantial decomposition of hydrocarbon constituents, separating thehydrogen sulphide from the gasoline stock, and thereby obtaining agasoline stock with reduced sulphur content and improved response totetraethyl lead.

WALTER A. SCHULZE.

